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Wheat Midge Emerging & 2018 Forecast (06/21/18)

Wheat midge emergence will be starting soon in the northern tier of North Dakota where it has been a major insect pest of hard red spring wheat and durum wheats.

Wheat Midge Emerging & 2018 Forecast

Wheat midge emergence will be starting soon in the northern tier of North Dakota where it has been a major insect pest of hard red spring wheat and durum wheats. The wheat midge degree day model predicts the emergence of wheat midge, and helps producers to determine when to scout and if their wheat crop is at risk (or in a susceptible wheat stage, heading to early flowering, for female wheat midge egg-laying). The degree day model using a base temperature of 40 F to predict the emergence of males at 1,100 accumulated growing degree days (AGDD), 1,300-1,600 AGDD for female wheat midge (see table below). See wheat midge AGDD map on next page.

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Producers can access the wheat midge degree day model on North Dakota Agricultural Weather Network (NDAWN) at:

https://ndawn.ndsu.nodak.edu/wheat-growing-degree-days.html

Select your nearest NDAWN station and enter your wheat planting date. The output indicates the expected growth stage of the wheat and whether is susceptible to midge infestation, as well as how far along the wheat midge emergence is, such as, 50% females emerged. Scouting for the orange adult flies is conducted at night when temperatures are greater than 59 F and the winds are less than

6 mph. Use a flash light and slowly scan the heads of wheat plants for wheat midge adults, counting the number of flies per head.

The economic thresholds for wheat midge are: one or more midge observed for every four or five heads on hard red spring wheat, or one or more midge observed for every seven or eight heads on durum wheat.

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2018 Wheat Midge Forecast: Two thousand and ten soil samples were collected from 21 counties in the fall of 2017 to estimate the regional risk for wheat midge in North Dakota for 2018. Results indicated low levels of overwintering wheat midge larvae (cocoons) (see map on next page). In fact, the 2018 wheat midge risk forecast is one of the lowest on record, since the survey started in 1995.

Less than one percent of the soil samples had economic population densities of wheat midge (greater than 500 midge larvae per square meter) this past year. The hot spot was located in one soil sample in northeast Rolette County in north central North Dakota. The majority of the soil samples, 75 percent, had no wheat midge cocoons. This is good news for North Dakota wheat producers as it will reduce the likelihood that insecticide inputs will be needed for wheat midge control in wheat in 2018.

Wheat midge populations ranged from zero to 1,321 midge larvae per square meter, with an average of 24 larvae per square meter in 2017. In 2016, wheat midge populations were slightly higher than 2017, ranging from zero to 2,071 midge larvae per square meter, with an average of 42 larvae per square meter. Other areas with low wheat midge populations (200 to 500 larvae per square meter) occurred in small, localized areas in northeastern Eddy and Wells, and south central Ramsey counties. These population levels are still considered non-economic and low risk for wheat midge.

The dry weather in the northwest and north central areas of North Dakota was extremely unfavorable for wheat midge in 2017. Larvae are susceptible to dryness and require dew or rain to drop out of the wheat heads and to dig into the soil to overwinter as cocoons. Even with the low risk forecast for wheat midge, it is wise to scout any wheat fields that are at risk from heading to early flowering (<50% flowering) during wheat midge emergence. Remember, scouting for wheat midge is still the best way to determine if you have an economic infestation in your wheat field and ‘good insurance.’

Thanks to the NDSU Extension Agricultural agents who collect the soil samples in their county each year. The North Dakota Wheat Commission provides funding to support the wheat midge survey.

For more information about wheat midge scouting and IPM, please consult the NDSU Extension IPM of the Wheat Midge in North Dakota E1330 (revised) and the Extension Entomology website on wheat midge.

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Janet J. Knodel

Extension Entomologist

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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